Method of forging



July 13, 1943. c. A. BRAUCHLER METHOD OF FORGING Filed June 23, 1941 2 Sheets-Sheet l umlllmll July 13, 1943. c. A. BRAUCHLE R METHOD OF FORGING Filed June 23, 1941 2 Sheets-Sheet 2 Patented July 13, 1943 UNlTED STATES PATENT ()FFlC 6 Claims.

The invention relates to a forging method and more particularly to a novel method of producing forgings for making crank case parts for radial motors such as are used in airplanes.

These forgings are generally circular in shape and provided with peripheral fianges on one or both sides, the flanges having longitudinal ribs at spaced intervals and having semi-circular cut-outs at their edges so that when two of these crank case parts are attached together the cylinders of the motor may be received in said cutouts.

The finished forging is then machined to size and shape. the ribs being cut away excepting at their outer ends forming in'turned flanges by means of which the tWo crank case parts are bolted together.

The present invention, however, is not concerned with the finished machined part, but only with the finished forging and the manner in which it is made.

Under present practice, such forgings are made from a substantially cubic billet or block of steel which is forged in a die into a disk of considerably less diameter and of considerably greater thickness than the finished article.

This partly finished product is then reheated and placed in a second die and forged into a further partly completed form after which it is reheated and placed in a third die and forged to the desired size and shape.

The object of the present improvement is to eliminate the preliminary forging steps and to provide a centrifugal cast blank which is reheated and placed in dies and forged to the finished forged shape desired.

Another object is to provide a method of forming a generally circular forging having a peripheral flange with spaced longitudinal ribs thereon. and semi-circular cut-outs in the edge of the flange between adjacent ribs, this forging being formed from a centrifugal cast substantially circular blank of greater thickness than the finished forging and provided with a peripheral flange of greater thickness and less height than the peripheral flange upon the forging, said flange having spaced projections at its edge of less height than the ribs upon the forg- A still further object is to form such a cast blank with a central opening and a some which is cut from the blank before the same is placed in the forging dies.

Another object is to form'acast blank of this character having a tong hold by means of which it may be manipulated in the forging dies.

The above objects together with others which will be apparent from the drawings and following description, or which may be later referred to, may be attained by carrying out the method in the manner illustrated in the accompanying drawings in which Figure 1 is a Vertical sectional view through a centrifugal casting machine in which the cast blank is made;

Fig. 2, a plan view of the cast blank;

Fig. 3, a transverse sectional view through the cast blank taken as on the line S'3, Fig. 2;

Fig. 4, a plan View of one side of the finished forging;

Fig. 5, a similar View of the other side of the forging;

Fig, 6, a transverse sectional view through the forging taken as on the line 6-6, Fig. 5; and

Fig. '7, a transverse sectional View through the finished machined crank case part.

Similar numerals refer to similar throughout the several views.

The cast blank may be centrifugally cast in a machine such as shown in Fi ure 1 comprising a metal turntable IE! mounted upon a Vertical shaft Ii journal-ed as at iii in a base [3 and provided with a pulley M which may be connected as by the belt 55 with a motor or other source of power for rotating the turntable at proper speed. A speed of about 450 R. P. M. may be used with very good results although it should be understood that it is not the intention to limit this operation to any exact speed since different conditions and circumstances may require considerable variation in the speed of rotation of the turntable.

This turntable is centrally recessed as indicated at 15 to receive the sand mold or core ll which is shaped to cooperate with the steel mold l3 to produce the desired shape in the castin to be made in the machine.

This steel mold rests upon the turntable from the recess It to the periphery thereof, as shown in Fig. l. The upper side of the metal mold l8 may be centrally recessed and shouldered as at [9 to receive the upwardly tapered 2t! which communicates with or casting recess 2!, and through which the molten metal is poured to fill the recesses of the molds.

The molding impressions or recesses within the sand mol-d l7 and steel mold 18 are so shaped as to produce the cast blank indicated generally at 22 in Figs. 1, 2 and 3 which is of substantially parts circular form having the central opening 23 which is slightly tapered toward the top as indicated in said figures and surrounded by the upwardly disposed annular flange 24 terminating in the inturned annular flange 25.

At the periphery of the casting is a depending annular flange 26 of considerable thickness having at spaced intervals around its edge the bosses or projections 21 preferably downwardly tapered as best shown in Fig. 3.

In some cases it is desirable to provide a somewhat similar peripheral flange 28 around the upper side of the cast blank where a flange is sometimes desired in the finished crank case part opposite to the flange 26.

For the purpose of manipulating the blank in forging dies, the mold parts may be recessed as at 29 to provide a radially dispose-d tong hold 30 extending outward from the cast blank in position to be gripped with tongs as in usual and wellalloy metal is poured through the sprue 29, while the turntable with the molds thereon is rotated at the desired speed.

The centrifugal action thus produced will cause the molten metal to be thrown outward from the center producing a solid casting free of pipes,

blow holes or impurities as the more solid metal is thrown outward by centrifugal force while the impurities will remain in the center.

When the casting is completed a tapered riser or gate 3| of considerable height and reduced diameter remains at the center of the casting containing the impurities and spongy metal, and this riser is sheared or punched from the central opening of the casting, leaving the cast blank as Shown in s. 2 and 3 of solid metal free from impurities.

The cast blank as shown in Figs. 2 and 3 is heated to forging temperature and placed in forging dies of desired contour and hammered to produce the finished forging shown in Figs. 4, 5 and 6, which may then be machined to produce the crank case part shown in Fig. '7.

The forging shown in Figs. 4 to 6, inclusive, is of the shape and size required for producing the machined part shown in Fig. 7, the tong hold 30 having been sheared or cut therefrom preparatory to machining.

In this forging it will be noted that the body portion 22a has been reduced in thickness in the forging operation and that the central opening 233. has been slightly enlarged and the flange 24a surrounding the same has been somewhat changed in shape.

It will also be seen that at the points where the bosses 21 are located upon the cast blank, the peripheral flange 26 of the blank has been elongated producing ribs 21a and that between these ribs the peripheral flange has been reduced in thickness as indicated at 26a and semi-circular cut outs 2% have been formed in the edge of the peripheral flange between adjacent ribs.

It will also be seen that the opposite peripheral flange 28 of the cast blank has been considerably elongated and tapered as shown at 28a.

To form the completed crank case part the forging as shown in Fig. 6 is then machined to the form shown in Fig. 7, the body portion being considerably reduced in thickness as indicated at 22c, the peripheral flange 26a being considerably reduced in thickness as at 26c.

The ribs 2'! are entirely cut away excepting at the ends forming the inturned angular flanges 210 at these points for connection to corresponding flanges upon a similar member to form the complete crank case.

The flange 28a is similarly reduced in thickness as indicated at 280 .with an inturned annular flange 28d at its edge, and the central flange 24a is reduced in thickness and changed in form as indicated at 240.

It should be understood that the form of the crank case parts shown is for the purpose of illustration only, as there are several modifications of the same which may be made by the same process.

In one form the flange 28c is eliminated entirely and in a double crank case a flange 260 is formed on each side of the member 220 so that in the finished crank case a part such as shown in Fig. '7 is attached to each side of t e doub e member providing for two radial rows of cylinders.

It should also be understood that although the invention is illustrated and described for the production of forgings for crank cases, it is applicable to the production of forgings for various other parts of generally similar form.

From the above it will be seen that the metal is refined and solidified in the centrifugal casting operation and then further refined and solidified by the hammering to which it is subjected in the forging operation.

I claim:

1. The method of forming a forging for a crank case and the like which consists in first centrifugally casting a circular blank having a peripheral flange provided at its edge with spaced bosses, the cast blank having a radial tong hold thereon, then heating the cast blank to forging temperature and placing it in forging dies and forging the hot blank reducing the thickness thereof and forming longitudinal ribs upon the peripheral flange at the points where the bosses are located and reducing the thickness of and elongating the flange between adjacent ribs.

2. The method of forming a forging for a crank case and the like which consists in first centrifugally casting a circular blank having a peripheral flange on one side, said flange being provided at its edge with spaced bosses, and a second peripheral flange on the other side of the cast blank, then heating the cast blank to forging temperature and placing it in forgin dies and forging the hot blank, reducing the thickness thereof and forming longitudinal ribs upon the first named peripheral flange at the points where the bosses are located and reducing the thickness of and elongating said flange between adjacent ribs, and reducing the thickness of and elongating said second peripheral flange.

3. The method of forming a forging for a crank case, which consists in first centrifugally casting a circular blank having a peripheral flang on one side, said flange being provided at its edge with spaced bosses, and a second peripheral flange on the other side of the cast blank, then heating the cast blank to forging temperature and placing it in forging dies and forging the hot blank, reducing the thickness thereof and forming longitudinal ribs upon the first named peripheral flange at the points where the bosses are located and reducing the thickness of and elongating said flange between adjacent ribs, and forming semi-circular cut outs in the edge of said flange between adjacent ribs, and reducing the thickness of and elongating said second peripheral flange.

4. The method of forming a crank case part, which consists in first centrifugally casting a circular blank having a peripheral flange provided at its edge with spaced bosses, then heating the cast blank to forging temperature and placing it in forging dies and forging the hot blank reducing the thickness thereof and forming longitudinal ribs upon the peripheral flange at the points where the bosses are located and reducing the thickness of and elongating the flange between adjacent ribs and forming semi-circular cut outs in the edge of the flange between adjacent ribs, then machining the forged blank reducing the thickness of said flange and cutting away the ribs except the outer ends thereof forming inturned angular flanges at the edge of the peripheral flange.

5. The method of forming a forging for a crank case and the like which consists in first centrifugually casting a circular blank having a peripheral flange provided at its edge with spaced bosses, the cast blank having a radial ton hold thereon, then heating the cast blank to forging temperature and placing it in forging dies and forging the hot blank reducing the thickness thereof and forming longitudinal ribs upon the peripheral flange at the points where the bosses are located and reducing the thickness of and elongating the flange between adjacent ribs, and forming semi-circular cut outs in the edge of the flange between adjacent ribs.

6. The method of forming a forging for a crank case and the like which consists in first casting a circular blank having a thick peripheral flange and bosses located at the edge thereof and then forging the hot blank forming longitudinal ribs on the flange at the points where the bosses are located and reducing and elongating the flange between the ribs.

CHARLES A. BRAUCHLER. 

